U.S. patent application number 09/735320 was filed with the patent office on 2002-06-13 for sheet inverting apparatus and method.
This patent application is currently assigned to Xerox Corporation. Invention is credited to Conrow, Brian R., Morrison, Elden R..
Application Number | 20020070497 09/735320 |
Document ID | / |
Family ID | 24955269 |
Filed Date | 2002-06-13 |
United States Patent
Application |
20020070497 |
Kind Code |
A1 |
Morrison, Elden R. ; et
al. |
June 13, 2002 |
Sheet inverting apparatus and method
Abstract
A method and apparatus for inverting sheets traveling through a
machine with an inverter having a reversing chute and a reversing
nip in the reversing chute. An incoming sheet is receiving into the
reversing chute. The reversing nip reverses the direction of travel
of the sheet and drives sheet out of the reversing chute. A gap is
opened in said reversing nip, while the outgoing sheet still
extends through the reversing nip. A subsequent incoming sheet is
received into the reversing chute and through the gap in the
reversing nip, while the outgoing sheet still extends through the
gap. The gap is closed after the outgoing sheet has exited the
reversing nip, such the reversing nip reverses the direction of
travel of the subsequent incoming sheet and drives the sheet out of
the reversing chute. The machine may be a printing or copying
machine.
Inventors: |
Morrison, Elden R.;
(Rochester, NY) ; Conrow, Brian R.; (Rochester,
NY) |
Correspondence
Address: |
John E. Beck
Xerox Corporation
Xerox Square 20A
Rochester
NY
14644
US
|
Assignee: |
Xerox Corporation
|
Family ID: |
24955269 |
Appl. No.: |
09/735320 |
Filed: |
December 12, 2000 |
Current U.S.
Class: |
271/186 |
Current CPC
Class: |
B65H 15/004 20200801;
G03G 15/234 20130101; B65H 2301/33312 20130101; B65H 29/12
20130101; Y10S 271/902 20130101 |
Class at
Publication: |
271/186 |
International
Class: |
B65H 029/00 |
Claims
What is claimed is:
1. A method of inverting sheets traveling through a machine with an
inverter having a reversing chute and a reversing nip in said
reversing chute, said method comprising the steps of: a) receiving
an incoming sheet into said reversing chute; b) reversing the
direction of travel of the incoming sheet with said reversing nip,
and driving the previously incoming sheet, which is now an outgoing
sheet, out of said reversing chute; c) opening a gap in said
reversing nip, while the outgoing sheet still extends through said
gap in said reversing nip; d) receiving a subsequent incoming sheet
into said reversing chute and through said gap in said reversing
nip, while the outgoing sheet still extends through said gap; e)
closing said gap in said reversing nip after the outgoing sheet has
exited said reversing nip, thereby acquiring drive of the
subsequent incoming sheet; and f) reversing the direction of travel
of the subsequent incoming sheet with said reversing nip, and
driving the subsequent incoming, which is now an outgoing sheet,
out of said reversing chute.
2. The method according to claim 1, further comprising the steps
of: repeating steps c) through f) for each subsequent incoming
sheet.
3. The method according to claim 1, further comprising the step of:
providing a reversing nip comprised of a drive roller and an idler
roller; wherein the step of opening a gap in step c) comprises
moving one of said drive roller and said idler roller away from the
other of said drive roller and said idler roller; and the step of
closing said gap in step e) comprises moving said one of said drive
roller toward and said idler roller into engagement with said other
one of said drive roller and said idler roller.
4. The method according to claim 1, further comprising the steps
of: providing a reversing nip comprised of a drive roller and an
idler roller; forming said drive roller with a semi-cylindrical
drive surface and a flat on one side thereof; opening a gap in step
c) by rotationally positioning said drive roller with said flat
facing said idler roller; closing said gap in step e) by rotating
said drive roller and engaging said drive surface with said idler
roller.
5. The method according to claim 1, further comprising the step of:
providing an input nip adjacent to said reversing chute; and
wherein steps a) and d) of receiving an incoming sheet comprise the
steps of: receiving the incoming sheet in said input nip and
driving the incoming sheet in a forward direction into said
reversing chute; acquiring drive of the incoming sheet with said
reversing nip in the forward direction, while the incoming sheet is
still being driven by said input nip.
6. The method according to claim 5, further comprising the step of
accelerating said reversing nip in said forward direction to a
sheet drive speed equal to a sheet drive speed of said input nip,
before acquiring drive of the incoming sheet with said reversing
nip.
7. The method according to claim 5, further comprising the step of:
providing an output nip adjacent to said reversing chute; and
wherein the step of driving an outgoing sheet out of said reversing
chute in steps b) and f) comprises the steps of: driving the
outgoing sheet in a reverse direction out of said reversing chute
and into said output nip; acquiring drive of the outgoing sheet
with said output nip in said reverse direction, while the outgoing
sheet is still being driven in said reverse direction by said
reversing nip.
8. The method according to claim 7, further comprising the step of
accelerating said reversing nip in said reverse direction to a
sheet drive speed equal to a sheet drive speed of said output nip,
before acquiring drive of the outgoing sheet with said output
nip.
9. The method according to claim 8, further comprising the step of
accelerating said reversing nip in said forward direction to a
sheet drive speed equal to a sheet drive speed of said input nip,
before acquiring drive of the incoming sheet with said reversing
nip.
10. The method according to claim 9, further comprising the steps
of: providing a reversing nip comprised of a drive roller and an
idler roller; forming said drive roller with a semi-cylindrical
drive surface and a flat on one side thereof; opening a gap in step
c) by rotationally positioning said drive roller with said flat
facing said idler roller and halting said drive roller in this
position; closing said gap in step e) by rotating said drive roller
and engaging said drive surface of said drive roller with said
idler roller.
11. The method according to claim 9, further comprising the steps
of: opening said gap in said reversing nip before a first of said
incoming sheets arrives at said reversing nip; receiving said first
incoming sheet into said reversing chute and through said gap in
said reversing nip.
12. The method according to claim 9, further comprising the step
of: sensing a point in time when a trailing edge of a said incoming
sheet is a predetermined distance upstream of said input nip and
timing the acceleration and deceleration of said reversing nip from
said point in time.
13. The method according to claim 7, wherein step c) of opening
said gap occurs after the output nip has acquired drive of the
outgoing sheet and before the subsequent incoming sheet arrives at
said reversing nip.
14. The method according to claim 7, wherein said input and output
nips are formed by a tri-roll having first, second and third
abutting rollers, the first and second rollers abut to form the
input nip, and the second and third rollers abut to form the output
nip.
15. The method according to claim 1, wherein said machine is an
electrostatographic reproduction machine.
16. A sheet inverter for inverting sheets traveling along a sheet
path in a machine, said inverter comprising: a sheet reversing
chute for receiving an incoming sheet; an idler roller in the
reversing chute; a drive roller abutting said idler roller to form
a reversing drive nip located in the reversing chute, such that the
reversing nip reverses the incoming sheet's direction of travel and
drives the previously incoming and now outgoing sheet in the
reverse direction out of the reversing chute; and a reversing nip
gap device for opening a gap between the drive roller and idler
roller before the outgoing sheet has exited the reversing nip, such
that a subsequent incoming sheet may pass through the gap in the
reversing nip while the outgoing sheet still extends through the
gap; wherein the gap device closes the gap after the outgoing sheet
has exited the reversing nip, such that the reversing nip reverses
the subsequent incoming sheet's direction of travel and drives the
previously incoming and now outgoing sheet in a reverse direction
out of the reversing chute.
17. An inverter according to claim 16, wherein the reversing nip
gap device comprises: a flat surface formed on a circumferencial
surface of the drive roller, with an arcuate portion of the
circumferential surface of the drive roller forming a drive
surface; and a controller that i) rotates the drive roller into a
gap position in which the flat surface faces the idler roller to
form the gap between the idler roller and the drive roller, and ii)
rotates the drive roller such that the drive surface engages the
idler roller to close the gap.
18. An inverter according to claim 17, further comprising: an input
drive nip that receives a sheet traveling along the sheet path and
drives the sheet into the reversing chute; and wherein the
controller accelerates the reversing nip in the forward direction
to a speed that matches a speed of the input nip before closing the
gap, whereby when the gap is closed the reversing nip drives the
incoming sheet in the forward direction further into the reversing
chute.
19. An inverter according to claim 18, wherein the controller
closes the gap before the incoming sheet has exited the input
nip.
20. An inverter according to claim 18, further comprising: an
output nip adjacent to the reversing chute, the output nip receives
the outgoing sheet from the reversing nip and drives the sheet out
of the inverter to continue along the sheet path; and wherein the
controller accelerates the reversing nip in the reverse direction
to a speed that matches a speed of the output nip, before the
outgoing sheet is received by the output nip.
21. An inverter according to claim 20, wherein the controller opens
the gap after the outgoing sheet is received in the output nip.
22. An inverter according to claim 21, wherein the controller
closes the gap before the incoming sheet has exited the input
nip.
23. An inverter according to claim 22, wherein the reversing nip
gap device further comprises a reversible electric motor drivingly
connected to the drive roller and operatively connected to the
controller to receive control signals therefrom.
24. An inverter according to claim 23, further comprising a sensor
located a predetermined distance upstream of the input nip, wherein
the sensor detects a trailing edge of an incoming sheet and sends a
corresponding signal to the controller; and the controller times
the acceleration and deceleration of the electric motor from a time
which it receives the signal from the sensor.
25. An inverter according to claim 16, wherein the machine is one
of a printing or copying machine.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an improved sheet inverting
method and apparatus for inverting sheets traveling through a
machine, for example, a printing or photocopying machine.
BACKGROUND OF THE INVENTION
[0002] As xerographic and other copiers and printers increase in
speed and become more automatic, it is increasingly important to
provide higher speed yet more economical, reliable and more
automatic handling of both the print sheets being printed by the
machine and the original document sheets being copied. It is also
desired to accommodate sheets which may vary widely in size,
weight, thickness, material, condition, humidity, age, etc. These
variations change the beam strength or flexural resistance and
other characteristics of the sheets. Yet, the desire for automatic
and high speed handling of such sheets without jams, misfeeds,
uneven feeding times, damaged sheets, smeared print or other
interruptions increases the need for reliability of all sheet
handling components. A sheet inverter is one such sheet-handling
component with particular reliability and speed limitation
problems.
[0003] Although a sheet inverter is referred to in the copier and
printer art as an "inverter", its function is not necessarily to
turn the sheet over (i.e., exchange one face for the other). Its
function may be to effectively reverse the sheet orientation in its
direction of motion. That is, to reverse the leading edge and
trailing edge orientation of the sheet. Typically in inverter
devices, the sheet is driven or fed by feed rollers, conveyors or
other suitable sheet driving mechanisms into a sheet-reversing
chute. By then reversing the motion of the sheet within the chute
and feeding it back out from the chute, the desired reversal of the
leading and trailing edges of the sheet in the sheet path is
achieved.
[0004] Depending on the location and orientation of the inverter in
a particular sheet path, the reversal of the leading and trailing
edges of the sheet may or may not also accomplish an inversion
(turning over) of the sheet. In some applications, for example,
where the "inverter" is located at the corner of a 90.degree. to
180.degree. bend in the copy sheet path, the inverter may be used
to prevent inversion of a sheet and thereby maintain the same face
of the sheet face-up before and after this bend in the sheet path.
On the other hand, if the entering and departing path of the sheet,
to and from the inverter, is in substantially the same plane, the
inverter will invert the sheet. Thus, inverters have numerous known
applications in the handling of either original document sheets or
print sheets (collectively referred to herein as "print sheets" or
simply "sheets") to selectively maintain and/or change the sheet
orientation.
[0005] Inverters are particularly useful in various systems for pre
or post collation copying or printing, for inverting the original
documents, or for maintaining proper collation of the print sheets.
The facial orientation of the sheet determines whether it will be
stacked in forward or reversed serial order. Generally, the
inverter is associated with a by-pass sheet path and gate so that a
sheet may selectively by-pass the inverter, in order to provide a
choice of inversion or non-inversion. Inverters are also useful in
inverting the sheet to print on and/or copy from both sides of the
sheet for duplex copying and printing.
[0006] In one type of known reversing chute inverter, the sheet is
fed into and then wholly or partially released from a positive
feeding grip roller pair or input nip into the reversing chute. The
sheet is then reacquired by a different feeding grip roller pair or
exit nip and is driven in the reverse direction to exit the
reversing chute. U.S. Pat. Nos. 3,944,212 and 4,078,789 are
examples of tri-roll type reversing chute inverters. A tri-roll
reversing chute inverter includes a set of three rollers (the
tri-roll) that defines the input and exit nips of the inverter. A
reversing pinch roll pair or reversing nip is located downstream of
the tri-roll in the reversing chute. The reversing nip reverses the
sheet's direction of travel and feeds the sheet into the output
nip.
[0007] In U.S. Pat. Nos. 3,944,212 and 4,078,789 cited above, the
reversing nip is rotated in the reverse direction only and is
maintained open as the copy sheet is fed into the reversing nip by
the input nip. A sensor just downstream of the input nip senses
when the trailing edge of the sheet has exited the input nip. When
it is sensed that the sheet has exited the input nip, the reversing
nip is activated to engage the sheet and drive the sheet in the
reverse direction into the exit nip. For a brief period, between
the time the sheet exits the input nip and is re-acquired by the
reversing nip, the sheet is not positively gripped by any feed nips
and is traveling freely under it's own momentum.
[0008] The inverters disclosed in U.S. Pat. Nos. 3,944,212 and
4,078,789 open a gap in the reversing nip by forming a flat on the
drive roller of the nip and stopping the drive roller with the flat
facing the idler roller. The sheet may then enter the gap between
the drive roller and the idler roller unimpeded. Once the trailing
edge of the sheet has cleared the input nip, then the drive roller
is rotated one revolution in the reverse direction. As the drive
roller is rotated one revolution, the cylindrical portion of the
drive roller contacts the idler roller, thereby pinching the sheet
therebetween and driving the sheet in the reverse direction into
the exit nip.
[0009] Any loss of positive gripping of the sheet by the feed
mechanism during inversion, even if only very briefly, increases
the reliability problems of such inverters. As the speed of the
printing or copying machine is increased, the time frame after the
sheet is released from the input nip within which the reversing nip
roller pair must re-acquire the sheet in order to reverse the
sheet's direction becomes very short. The speed at which the
reversing nip roller pair can engage the copy sheet is limited by
the mass of the rollers and other factors that will be apparent to
those of skill in the art. As a result, there is a maximum sheet
speed beyond which the reversing nip rollers will not be able to
close quickly enough to re-acquire the sheet. In which case, the
sheet will clear the reversing nip and become jammed in the
reversing chute.
[0010] As the overall machine speed increases, the speed at which
the sheet enters and exits the reversing chute also increases. In
U.S. Pat. Nos. 3,944,212 and 4,078,789 cited above, the reversing
nip rotates in the reverse direction only, and must rotate more
quickly as sheet speed increases in order to re-acquire the sheet
and feed it into the exit nip within the available time frame.
Thus, as the overall machine speed increases, the speed
differential between the reversing nip and the copy sheets also
increases. When the reversing nip engages the copy sheet at higher
and higher speed differentials, the likelihood that the reversing
nip will scuff, buckle, tear and/or otherwise damage the sheet
increases.
[0011] Some devices have attempted to solve the above mentioned
problem by providing a reversing nip that applies a constant
reverse drive force upon the sheet that is less than the forward
drive force applied to the sheet by the input nip. The drive roll
in the reversing nip of such an inverter is always in contact with
the idler roll and is always rotating in the reverse direction.
Once the trailing edge of the sheet exits the input nip, the sheet
is virtually immediately reversed by the reversing nip and driven
into the exit nip. U.S. Pat. Nos. 4,359,217 and 4,346,880 are
examples of such constant return force reversing nip inverters. The
constant return force and friction applied to the sheet by the
reversing nip drive roller in his type of arrangement, however, may
scuff, buckle, tear, smear or otherwise damage the sheet,
particularly as speeds increase.
[0012] Other prior art reversing chute inverters, such as disclosed
in U.S. Pat. No. 4,487,506, the disclosure of which is hereby
incorporated herein as of reference, provide a reversing nip roller
pair in the reversing chute. Referring now to FIG. 1, the sheet
enters the inverter 1 through the input nip 3 and is positively
driven by the input nip into the reversing nip 5. The reversing
nip, which is rotating in the forward direction at the same speed
as the input nip, acquires the leading edge of the sheet (not
shown) before the trailing edge of the sheet exits the input nip.
Since the reversing nip 5 takes up the drive of the sheet at the
same speed as the input nip, the reversing nip will not scuff,
tear, mark, smear or otherwise damage the sheet. When the trailing
edge of the sheet exits the input nip the reversing nip is
decelerated, halted and accelerated in the reverse direction and
drives the sheet in the reverse direction into the exit nip 7. The
reversing nip is accelerated to the same speed as the exit nip
before the leading edge of the sheet enters the exit nip. The exit
nip therefore acquires the leading edge of the sheet before the
trailing edge of the sheet exits the reversing nip without
scuffing, buckling, tearing, smearing or otherwise damaging the
sheet. This type of inverter maintains constant drive control of
the sheet and relatively gently decelerates and reverses direction
of the sheet.
[0013] The reversing nip described in the preceding paragraph
substantially overcomes many of the sheet control and damage
problems of previous reversing chute inverters. However, this type
of forwarding reversing nip has a built in speed limitation. The
trailing edge of a first or preceding sheet must exit the reversing
nip 5 and the reversing nip must decelerate, reverse direction and
accelerate to the input nip speed in the forward direction before
the leading edge of a second or following sheet reaches the
reversing nip. If the reversing nip 5 has not reached the same
speed as the speed of the input nip 3 before the leading edge of a
following sheet reaches the reversing nip, then the following sheet
is likely to be scuffed, torn, buckled, smeared and/or jammed in
the reversing chute.
SUMMARY OF THE INVENTION
[0014] One form of the present invention provides a method of
inverting sheets traveling through a machine with an inverter
having a reversing chute and a reversing nip in the reversing
chute, the method comprising the steps of: a) receiving an incoming
sheet into the reversing chute; b) reversing the direction of
travel of the incoming sheet with the reversing nip, and driving
the previously incoming sheet, which is now an outgoing sheet, out
of the reversing chute; c) opening a gap in the reversing nip,
while the outgoing sheet still extends through the gap in the
reversing nip; d) receiving a subsequent incoming sheet into the
reversing chute and through the gap in the reversing nip, while the
outgoing sheet still extends through the gap; e) closing the gap in
the reversing nip after the outgoing sheet has exited the reversing
nip, thereby acquiring drive of the subsequent incoming sheet; and
f) reversing the direction of travel of the subsequent incoming
sheet with the reversing nip, and driving the subsequent incoming,
which is now an outgoing sheet, out of the reversing chute.
[0015] Another form of the present invention provides a sheet
inverter for inverting sheets traveling along a sheet path in a
machine, the inverter comprising: a sheet reversing chute for
receiving an incoming sheet; a reversing drive nip, formed of a
drive roller abutting an idler roller, located in the reversing
chute, such that the reversing nip reverses the incoming sheet's
direction of travel and drives the previously incoming and now
outgoing sheet in the reverse direction out of the reversing chute;
and a reversing nip gap device for opening a gap between the drive
roller and idler roller before the outgoing sheet has exited the
reversing nip, such that a subsequent incoming sheet may pass
through the gap in the reversing nip while the outgoing sheet still
extends through the gap; wherein the gap device closes the gap
after the outgoing sheet has exited the reversing nip, such that
the reversing nip reverses the subsequent incoming sheet's
direction of travel and drives the previously incoming and now
outgoing sheet in a reverse direction out of the reversing
chute.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] One form of the present invention will now be described, by
way of example, with reference to the appended drawings, of
which:
[0017] FIG. 1 is a diagrammatic side view of a prior art tri-roll
inverter apparatus;
[0018] FIG. 2 is a diagrammatic side view of an exemplary
xerographic printing system employing tri-roll inverters;
[0019] FIG. 3 is an enlarged diagrammatic side view of a tri-roll
inverter employing a segmented reversing nip roller pair according
to one form of the present invention; and
[0020] FIGS. 4 though 9 are serial views illustrating the passage
of two consecutive sheets through the inverter of FIG. 3.
DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION
[0021] Referring now to FIG. 2, there is shown a schematic
illustration of an exemplary xerographic printing machine 10 that
employs inverters 12, 14 according to one form of the present
invention. The illustrated printing machine includes a conventional
photoconductive layer or light sensitive surface 16 on a conductive
backing in the form of a belt 18. The belt is mounted on a
plurality of rollers journaled in a frame (not shown), in order to
rotate the belt and cause the photoconductive surface 16 to pass
sequentially through a plurality of xerographic process stations A
through E. It should be understood that a drum photoreceptor and/or
flash exposure could be employed in place of the photoreceptor belt
and exposure means illustrated in FIG. 2.
[0022] For purposes of the present disclosure, the several
generally conventional xerographic processing stations in the path
of movement of the photoconductive surface 16 may be as follows. A
charging station A, where the photoconductive surface of the
xerographic belt 18 is uniformly charged. An exposure station B,
where a light or radiation pattern of a document to be printed is
projected onto the photoconductive surface to expose and discharge
select areas of the photoconductive surface to form a latent image
thereon. A developing station C, where xerographic developer is
electrostatically applied to the photoconductive surface of the
drum to generate a toner image on the photoconductive surface. A
transfer station D, where the toner image is electrostatically
transferred from the photoconductive surface to a print sheet.
Finally, a cleaning station E, where the photoconductive surface is
brushed or otherwise cleared of residual toner particles remaining
thereon after image transfer. In order to generate multi-color
prints, there may be a group of process stations A through C for
each of a plurality of colors. For example, there may be a group of
stations A through C for each of yellow, cyan, magenta and
black
[0023] Print sheets supplied from a sheet feeding tray or sheet
feeding module 20, are fed by a series of sheet feeding rollers and
guide rails to the transfer station D. At the transfer station, the
developed toner image is transferred from the photoconductive belt
18 to the sheet. The sheet is then stripped from the photoreceptor
belt by a sheet stripper 22 and transported to a fusing station F,
where a fuser 24 fuses the toner image onto the print sheet in a
known manner. The print sheet, which now has an image fused to a
first face thereof, is then transported by a plurality of rollers
to a first gate 26. The first gate either diverts the sheet into a
duplexing module 28 for two-sided or duplex copying, or allows the
sheet to continue on toward an output tray or stacking module 30
for one-sided or simplex copying. On its way to the stacking
module, the sheet passes a second gate 32 that either diverts the
sheet into an output inverter 14 for inversion prior to entering
the stacking module, or allows the sheet to pass directly into the
stacking module without inversion.
[0024] A sheet that is diverted by the first gate 26 into the
duplexing module 28 is inverted by a duplex inverter 12. Following
inversion, the sheet is returned to the transfer station D to
receive a second toner image on the second face thereof from the
photoconductive belt. The second toner image is fused to the sheet
at the fusing station F and the first gate allows the sheet to be
conveyed toward the stacking module 30. The sheet may pass directly
into the stacking module 30 or be diverted by the second gate 32
into the output inverter 14 for inversion prior to entering the
stacking module.
[0025] A programmable machine controller 40, such as the controller
disclosed in U.S. Pat. No. 3,940,210, the disclosure of which is
incorporated herein by reference, is used to control the operation
of xerographic machine 10 in either the simplex or duplex modes.
Alternatively, conventional counters and circuitry as disclosed in
U.S. Pat. No. 3,588,472, the disclosure of which is incorporated
herein by reference, could be used to carry out the invention as
disclosed herein.
[0026] An output inverter 14 according to one form of the present
invention is schematically illustrated in side view in FIG. 3. The
illustrated inverter comprises an improved tri-roll reversing chute
type inverter. Three rollers 41, 42, 43 form the tri-roll. Rollers
41 and 42 of the tri-roll meet to form an input nip 44 and rollers
42 and 43 of the tri-roll meet to form an output nip 46. A
reversible pair of rollers, namely, a segmented drive roller 50 and
an idler roller 52, forms a reversing nip 54. The reversing nip is
located in a reversing chute 55. The drive roller 50 of the
reversing nip is segmented, meaning the drive roller has a
semi-cylindrical peripheral drive surface 56 with a cutout or flat
spot 58 on one side. The reversing nip's drive roller is driven by
a variable speed, reversible drive motor (not shown) that is
connected to the drive roller 50 through a suitable coupling (not
shown). With this construction, the drive roller 50 can be driven
in a clockwise or counterclockwise direction at variable speed,
depending on the control signal received from the controller, as
will be described in further detail hereinafter. A plurality of
guide rails 60 guide the print sheets along the paper path between
a plurality drive nips 62.
[0027] The passage of two consecutive sheets, e.g. a leading sheet
S and a following sheet S', through the inverter of FIG. 3 is
serially illustrated by FIGS. 4 through 9. When inversion of a
sheet S traveling from the fuser to the stacking module is not
desired, the second gate 32 is placed in a non-inverting position
illustrated by dashed lines in FIGS. 3 through 9. When the second
gate is in the non-inverting position the sheet is allowed to pass
directly to the stacking module 30 (see FIG. 2) via an inverter
by-pass path 80.
[0028] When it is desired to invert the print sheet before it
enters the stacking module 30, the second gate 32 is moved into an
inverting position shown in solid lines in FIGS. 3 through 9. When
in the inverting position, the second gate intercepts the print
sheet S traveling from the fuser 24 toward the stacking module and
diverts the sheet into the output inverter 14 as illustrated in
FIG. 4. Guide rails direct the leading edge of the sheet into the
input nip 44. The input nip acquires the sheet S and drives the
sheet into the reversing chute 55.
[0029] Prior to entry of the sheet S into the reversing chute 55,
the drive roller 50 of the reversing nip 54 is positioned and
stopped in a gap position, in which the flat 58 faces the idler
roller 52. When the drive roller is in the gap position, a gap 59
is formed in the reversing nip between the drive roller and the
idler roller. The drive roller is maintained in the gap position to
await the arrival of an incoming sheet. The leading edge of an
incoming sheet S may pass unimpeded into and through the gap 59 in
the reversing nip, as illustrated in FIG. 4. Before the trailing
edge of the sheet S exits the drive nip 44, the drive roller 50 of
the reversing nip 54 is accelerated in a forward direction, as
indicated by arrow R, to a sheet drive speed that is equal to the
sheet drive speed of the input nip 44. The semi-cylindrical drive
portion 56 of the drive roller engages the idler roller 52 at the
same speed as the input nip, thereby closing the gap and acquiring
drive of the sheet S as shown in FIG. 5. The reversing nip is
thereby closed and acquires drive of the sheet S before the
trailing edge of the sheet exits the input nip 44.
[0030] Once the tailing edge of the sheet S has exited the input
nip 44, the reversing nip 54 is decelerated and stopped, with the
trailing edge of the sheet clear of a guide wedge 82 as shown in
FIG. 6. In the illustrated embodiment, the reversing chute 55 is
curved away from the output nip 46, i.e. to the left in FIGS. 4
through 9. With this construction, the beam strength of the sheet S
causes the sheet to straighten in the reversing chute, as indicated
by arrow Y in FIG. 6. When the sheet straightens, the trailing edge
of the sheet moves from the input side to the output side of the
guide wedge 82. The reversing nip 54 is then accelerated in the
reverse direction, as shown by arrow R' in FIG. 7, and drives the
previously trailing and now leading edge of the sheet S into the
output nip 46. The reversing nip is accelerated to a sheet drive
speed that is equal to the sheet drive speed of the output nip
before the now leading edge of the sheet reaches the output
nip.
[0031] The spacing between the reversing nip 54 and the output nip
46 is set at approximately the same distance as the spacing between
the input nip 44 and the reversing nip 54. With this construction,
when driving the sheet S in the reverse direction, the drive roller
50 will rotate to the gap position shortly after the output nip 46
has acquired positive drive of the sheet S. The drive roller 50 is
then halted in the gap position, such that the gap 59 is again
formed in the reversing nip 54. The drive roller is maintained in
the gap position to await the arrival of a subsequent or following
sheet S'. The gap 59 allows the leading edge of a following sheet
S' to enter the reversing nip, while the now trailing edge of the
leading sheet S is still extending through the gap as shown in FIG.
8. The leading sheet S and the following sheet S' thus overlap in
the gap 59 in the reversing nip and in the reversing chute 55. The
larger the sheets S and S' are from leading to trailing edge, the
larger the degree of overlap will be in the reversing chute.
[0032] Once the now trailing edge of the leading sheet S clears the
reversing nip 54, the reversing nip is accelerated in the forward
direction R to the speed of the input nip 44. The reversing nip
closes and acquires the following sheet S', as illustrated in FIG.
9, at the same sheet drive speed as the input nip. The following
sheet S' now becomes a leading sheet in relation to the next
following sheet (not shown) and the cycle illustrated in FIGS. 4
through 9 is repeated with each subsequent following sheet.
[0033] As described above, the sheet S is only driven in the
forward direction by the reversing nip 54 from a point just prior
to release of the sheet by the input nip 44 (as shown in FIG. 5) to
the point where the trailing edge of the sheet clears the guide
wedge 82 (as shown in FIG. 6). The length of the arc formed by
semi-cylindrical drive portion 56 of the reversing nip drive roller
50 must therefore be at least as long as the distance the sheet
travels between these two points. The length of the arc on the
drive roller is determined by appropriately selecting the diameter
of the drive roller and the depth of the flat 58. For example, if
the distance between the input nip 44 and the desired flip point of
the trailing edge of the sheet S (see sheet S in FIG. 6) were 3
inches, then the semi-cylindrical drive portion 56 could be formed
with an arc having a length of about 4 inches. A 4 inch arc 56
would incorporate an optional safety factor of 1 inch. To achieve
this, a 1.75 inch diameter roll having a total circumference of 5.5
inches could be utilized. Removal of about 25% of the roll would
result in a flat 0.44 inches deep and leave the required arc.
[0034] Sensors 70, 72, and 74 (see FIG. 3) sense the leading and/or
the trailing edges of the sheets as the sheets travel through the
inverter and forward corresponding signals to the controller. The
sheet sensors 70, 72, and 74 are strategically placed along the
sheet path in the output inverter 14, in order to facilitate
control of the drive rollers in the inverter by the controller. The
first sensor 70 is located a predetermined distance upstream of the
inverter. The first sensor detects the leading edge of a sheet
entering the inverter 14 and delivers a corresponding signal to the
controller. After a predetermined delay period has elapsed
following detection of the leading edge of the sheet by the first
sensor, the controller initiates an acceleration of the sheet
within the inverter from an image process speed to an inversion
speed.
[0035] The second sensor 72 is located a predetermined distance
upstream of the input nip 44. The second sensor detects the
trailing edge of a sheet S traveling through the inverter 14 and
sends a corresponding signal to the controller.
[0036] After a first predetermined delay period has elapsed
following detection of the trailing edge of an incoming sheet S by
the second sensor 72, the controller initiates an acceleration of
the reversing nip drive roller 50 in the forward direction R, as
illustrated in FIG. 4. The acceleration of the drive roller is
timed and controlled such that the reversing nip 54 closes and
acquires the incoming sheet S at the same speed as the sheet is
being delivered by the input nip 44, as shown in FIG. 5.
[0037] The controller then initiates a deceleration of the
reversing nip 54 after a second predetermined delay period
following detection of the trailing edge of the sheet S by the
second sensor 72. The second delay period is set to initiate
deceleration after the trailing edge of the sheet has exited the
input nip 44. The deceleration is controlled such that the sheet S
is brought to rest with its trailing edge clear of the guide wedge
82, as depicted in FIG. 6.
[0038] Next, after a third delay period following detection of the
sheet's trailing edge by the second sensor, the controller
initiates an acceleration of the drive roller 50 in the reverse
direction R' and drives the sheet into the output nip 46, as
depicted in FIG. 7. The third delay period is set to provide a
dwell time after the sheet has been stopped clear of the guide
wedge, in order to enable the sheet to straighten as depicted by
arrow Y in FIG. 6. The acceleration of the drive roller in the
reverse direction R' is controlled such that the reversing nip 54
delivers the sheet to the output nip at the same speed as the
output nip drives the sheet. Finally, the controller brings the
drive roller 50 to rest in the gap position, with the flat 58
facing the idler roller 52, to await the arrival of a subsequent
incoming sheet S', as shown in FIG. 8.
[0039] The third sensor 74 is located in the reversing chute 55, in
order to detect a sheet that has become jammed or otherwise stuck
in the reversing chute and send a corresponding signal to the
controller. The controller then executes a typical jam shutdown and
alarm sequence, thereby preventing further sheets from becoming
jammed and alerting the operator of the jam.
[0040] The duration of the various delay periods described above
will depend upon numerous factors. Some of these factors are, how
far the first sensor is from the inverter, how far the second
sensor is from the input nip and the reversing nip, how far the
reversing nip is from the input nip and the output nip, the length
of the drive surface 56 on the drive nip, and the magnitude of the
processing and inverting speeds, as will be well understood by one
of skill in the art.
[0041] A specific arrangement of sensors and the interaction of the
sensors with the controller has been described above. One of skill
in the art will appreciate, however, that other arrangements of
sensors may be employed to achieve the desired result with a
segmented reversing nip inverter according to the present
invention. The disclosed arrangement and use of sensors is an
exemplary arrangement. The present invention is not intended to be
limited to the specific arrangement and use of sensors that is
illustrated and described, but to include all such alternatives
that are compatible with the claimed invention.
[0042] The invention has been described by way of example with
reference to the output inverter 14 as illustrated in FIGS. 3
through 9. The duplex inverter 12 (FIG. 2) is similar to the output
inverter, except that duplex inverter does not include an inverter
bypass path 80 (FIG. 3) or an associated gate. Since only sheets
requiring inversion for duplex printing or copying are directed
into the duplexing module 28 by the first gate 26 (FIG. 2), all the
sheets traveling through the duplexing module require inversion and
must pass through the duplex inverter. Therefore, the duplex
inverter does not require an inverter bypass path and gate.
Furthermore, the first sensor 70 may be located in the duplexing
path upstream of the duplex inverter 12, such that the sheets are
accelerated to inversion speed prior to arriving at the duplex
inverter. Such an arrangement enables the inverter to operate at a
constant speed, i.e. inversion speed, and simplifies the control of
the inverter.
[0043] As described above, the formation of a gap in the reversing
nip enables an incoming following sheet to overlap an outgoing
leading sheet in the reversing nip in the reversing chute. The
present invention thus enables a following sheet to follow more
closely behind a leading sheet than in prior art inverters. In the
prior art inverter of FIG. 2, a leading sheet must clear the
forwarding reversing nip. The forwarding reversing nip must then be
decelerated from the speed of the output nip in the reverse
direction, stopped and accelerated in the forward direction to the
speed of the input nip, all before the following sheet enters the
reversing nip. Thus, the timing latitude and speed in sheets per
minute are both increased by employing an inverter according to the
present invention. As the length of the sheets from leading to
trailing edge increases, the sheets overlap to a greater extent in
the gap and in the reversing nip. Therefore, the gains in timing
latitude and sheet speed increase compared to prior art inverters
as sheet length increases.
[0044] One of skill in the art will appreciate that a segmented
reversing roll according to the present invention may be used in
reversing chute type inverters that do not utilize a tri-roll to
form the input and output nips. For example, the input and output
nips may be formed by respective input and output roller pairs, as
illustrated in U.S. Pat. No. 3,416,791, the disclosure of which is
hereby incorporated herein as of reference, rather than by a
tri-roll arrangement.
[0045] It will also be appreciated that, rather than segmenting the
drive roller, one of the idler roller and the drive roller of the
reversing nip may be selectively moved away from and into
engagement with the other, in order to selectively provide the gap
and drive the sheets. Various mechanisms capable of moving one of
the rollers away from and into engagement with the other are well
known in the art, for example, see previously incorporated U.S.
Pat. No. 3,416,791, and are therefore not described herein.
[0046] The reverse nip is disclosed herein as having a drive roller
that is driven by a reversible variable speed motor. The reversal
of direction of the drive roller may alternatively be achieved by
employing a non-reversible motor drivingly connected to the drive
roller via any suitable mechanism capable of reversing the drive
applied to the drive roller by the motor. For example, a suitably
geared transmission or two clutch drive mechanism may be employed.
Previously mentioned U.S. Pat. No. 4,487,506, which is incorporated
herein as of reference, discloses alternative mechanisms capable of
reversing the rotation of a drive roller in a drive nip roller
pair.
[0047] In addition to the method and apparatus disclosed above,
other modifications and/or additions will be readily apparent to
those skilled in the art upon reading this disclosure. All such
modification and additions are intended to be encompassed within
the invention disclosed and claimed herein.
* * * * *